Variable valve actuation system having a crank-based actuation transmission

ABSTRACT

A variable valve actuation system having a crank-based eccentric transmission driven by an electric motor to control valve lift, duration, and phasing in the cylinder head of an internal combustion engine. A rocker sub-assembly for each valve is pivotably disposed on a pivot shaft between the camshaft and the roller finger follower roller. A primary control crankshaft includes the pivot shaft and is itself rotated about its axis by a connecting rod driven by a motorized secondary crank mechanism to displace the rocker sub-assembly pivot shaft along an arcuate path to change the angular relationship of the rocker sub-assembly to the camshaft, thus changing the valve opening and closing timing and valve lift.

RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS

The present application is a Continuation-In-Part of a pending U.S. patent application Ser. No. 11/294,223, filed Dec. 5, 2005, and published as US Patent Application Publication, No. US 2007/0125329 A1.

TECHNICAL FIELD

The present invention relates to valvetrains of internal combustion engines; more particularly to devices for controlling the timing and lift of valves in such valvetrains; and most particularly to a system for variable valvetrain actuation (SVVA) interposed between the engine camshaft and the valve train cam followers to vary the timing and amplitude of follower response to cam rotation, wherein the SVVA is variably positioned by a crank mechanism, preferably an electromechanical eccentric variable valve actuation transmission (EVVAT).

BACKGROUND OF THE INVENTION

One of the drawbacks inhibiting the introduction of a gasoline Homogeneous Charge Compression Ignited (HCCI) engine in production has been the lack of a simple, cost effective, and energy-efficient Variable Valvetrain Actuation (VVA) system to vary one or both of the intake and exhaust events. Many electro-hydraulic and electro-mechanical “camless” VVA systems have been proposed for gasoline HCCI engines, but while these systems may consume less or equivalent actuation power at low engine speeds, they typically require significantly more power than a conventional fixed-lift and fixed-duration valvetrain system to actuate at mid and upper engine speeds. Moreover, the cost of these “camless” systems usually is on par with the cost of an entire conventional engine itself.

As the cost of petroleum continues to rise from increased global demands and limited supplies, the fuel economy benefits of internal combustion engines will become a central issue in their design, manufacture, and use at the consumer level. In high volume production applications, applying a continuously variable valvetrain system to just the intake side of a gasoline engine can yield fuel economy benefits up to 10% on Federal Test Procedure—USA (FTP) or New European Driving Cycle (NEDC) driving schedules, based on simulations and vehicle testing. HCCI type combustion processes have promised to make the gasoline engine nearly as fuel efficient as a conventional, 4-stroke Diesel engine, yielding gains as high as 15% over conventional (non-VVA) gasoline engines for these same driving schedules. The HCCI engine could become strategically important to countries dependent on a gasoline-based transportation economy.

Likewise, the use of a continuously variable valvetrain for both the intake and exhaust sides of a diesel engine has been identified as a potential means to reduce the size and cost of future exhaust aftertreatment systems and as a way to restore the lost fuel economy that these systems presently impose. By varying the duration of intake lift events, potential Miller cycle-type fuel economy gains are feasible. Also, with VVA on the intake side, the effective compression ratio can be varied to provide a high ratio during startup and a lower ratio for peak fuel efficiency at highway cruise conditions. Without intake side VVA, compression ratios must be compromised in a tradeoff between these two extremes. Exhaust side VVA can improve the torque response of a diesel engine. Varying exhaust valve opening times can permit faster transitions with the turbocharger, thereby reducing turbo lag. Exhaust VVA can also be used to expand the range of engine operation wherein pulse turbo-charging can be effective. Furthermore, varying exhaust valve opening times can be used to raise exhaust temperatures under light load conditions, significantly improving NOx adsorber efficiencies.

VVA devices for controlling the timing of poppet valves in the cylinder head of an internal combustion engine are well known.

U.S. Pat. No. 5,937,809 discloses a Single Shaft Crank Rocker (SSCR) mechanism wherein an engine valve is driven by an oscillatable rocker cam that is actuated by a linkage driven by a rotary eccentric, preferably a rotary cam. The linkage is pivoted on a control member that is in turn pivotable about the axis of the rotary cam and angularly adjustable to vary the orientation of the rocker cam and thereby vary the valve lift and timing. The oscillatable cam is pivoted on the rotational axis of the rotary cam.

U.S. Pat. No. 6,311,659 discloses a Desmodromic Cam Driven Variable Valve Timing (DCDVVT) mechanism that includes a control shaft and a rocker arm. A second end of the rocker arm is connected to the control shaft. The rocker arm carries a roller is for engaging a cam lobe of an engine camshaft. A link arm is pivotally coupled at a first end thereof to the first end of the rocker arm. An output cam is pivotally coupled to the second end of the link arm, and engages a corresponding cam follower of the engine. A spring biases the roller into contact with the cam lobe and biases the output cam toward a starting angular orientation.

A shortcoming of these two prior art VVA systems is that both the SSCR device and the DCDVVT mechanism include two individual frame structures per each engine cylinder that are somewhat difficult to manufacture.

Another shortcoming is that these mechanisms “hang” from the engine camshaft and thus create a parasitic load. The SSCR input rocker is connected through a link to two output cams that also ride on the input camshaft. Because the mechanism comprises four moving parts per cylinder, it is difficult to provide a return spring stiff enough for high-speed engine operation that can still fit in the available packaging space.

Still another shortcoming is that assembly and large-scale manufacture of such an SSCR device would be difficult at best with its large number of parts and required critical interfaces.

U.S. Pat. No. 6,997,153 discloses a drive system for continuously changing lift characteristics of the charge-cycle valves while the engine is in operation. The drive consists of a housing, a cam, an intermediate element, and a valve-actuating output element. The cam is mounted in the housing, for example, in the cylinder head, in a turning joint and actuates the intermediate element which also is mounted in a turning joint in the housing. The intermediate element is connected to the output element via a cam joint formed at the contact point of the intermediate element, having a base circle portion (stop notch) and a control section, and the output element which may include a follower roller. The output element is also mounted in a turning joint in the housing and transmits motion to a valve stem. A change in valve lift characteristics is effected by changing the position of the cam joint or the output element turning joint via an eccentric element in the housing for both the intermediate element and the output element.

No indication is provided of a practical structure for implementing this arrangement. However, significant manufacturing and control complexity would exist in providing for, and controlling the action of, eccentric control shafts for both the intermediate and output elements.

Several prior art VVA innovations, such as is disclosed in U.S. Pat. No. 7,252,058, employ a movable control arm or carrier assembly to vary valve lift, duration, and phasing in a dependent manner at one or more banks of engine valves.

U.S. Pat. No. 5,937,809 discloses carrier frame links pivoted via pairs of teeth between the carrier frames and a control shaft, running parallel to the camshaft. While this concept affects a nice linear relationship between the actuator control shaft and the carrier rotational positions, the gears are costly to make and present a backlash concern, given the oscillating nature of the mechanisms' torque loads.

In the variable valve timing mechanism disclosed in U.S. Pat. No. 6,019,076, the carrier frame elements are rotated through a pin, sliding bushing, and slotted fork arrangement. The slots are machined into the frame elements, slightly offset from the frame element pivot centers. The sliding bushings are pivoted on pins offset and parallel to the camshaft and control shaft. This arrangement requires careful grinding of the carrier slots to limit backlash, and the alignment of the control shaft pins is critical to ensure ease of assembly. Finally, inherent to any sliding bushings is a loss of actuation efficiency to compete with the fuel economy savings potential of the variable valve train mechanism itself.

U.S. Pat. No. 7,252,058 discloses inclusion of a slotted fork into the drive control shaft and replacement of the sliding bushing with a roller connected to the armed frame carrier. While this approach eliminates the parasitic friction of the previous forked design, the apparatus still requires a costly grind of the slot to limit lash to an acceptable level.

What is needed in the art is a simplified VVA mechanism that is not mounted on the engine camshaft, is easy to manufacture and assemble, requires only a single angular control element, and requires minimal packaging space in an engine envelope.

It is a principal object of the present invention to provide variable opening timing, closing timing, and lift amplitude in a bank of engine intake and/or exhaust valves.

It is a further object of the invention to simplify the manufacture and assembly of a VVA system for such variable opening, closing, and lift.

It is a still further object of the invention to provide such a system which is not parasitic on the engine camshaft.

SUMMARY OF THE INVENTION

Briefly described, the present invention provides a simple crank mechanism for transferring the rotary motion of an electric motor or similar actuator into useful motion to control the poppet valve lift profiles produced by a mechanical VVA system in the cylinder head of an internal combustion engine. The system varies valve lift, duration, and phasing in a dependent manner for one or more banks of engine valves. Using a single electrical rotary actuator per bank of valves to control the device, the valve lift events can be varied for either the exhaust or intake banks. Two such systems are required to accommodate both the exhaust and intake banks of valves.

The SVVA comprises a hardened steel rocker subassembly for each valve (or valve pair) pivotably disposed in needle roller bearings on a pivot shaft disposed between the engine camshaft and the engine roller finger follower. A primary control crankshaft supports the pivot shaft for controlling a plurality of valve trains for a plurality of cylinders in an engine bank. The primary control crankshaft is itself rotated about its axis by a secondary crank mechanism having an eccentric motion to displace the rocker subassembly pivot shaft along an arcuate path and hence to change the angular relationship of the rocker subassembly to the camshaft, thus changing the valve opening, closing, and lift. Valve actuation energy still comes from a mechanical camshaft that is driven from the engine by a belt or chain, and the electrical eccentric actuator receives its energy from the engine's alternator.

The present invention improves on the SVVA system disclosed in the pending parent U.S. patent application Ser. No. 11/294,223, filed Dec. 5, 2005 in the following way.

In the parent invention, the rocker sub-assembly positioning primary crankshaft is rotated directly by attachment to an electric motor with or without an intervening transmission. Prevention of lash requires an inefficient worm gear transmission.

In the present invention, the primary crankshaft is rotated by a secondary crank mechanism, preferably in the form of an eccentric transmission attached to the SVVA's control shaft arms. The eccentric actuator positively rotates the primary control crankshaft without lash and eliminates torque loads transferred back to the actuator at the two end states (highest and lowest valve lift) of the VVA system's operation by placing those states at the top dead center and bottom dead center positions of crank eccentricity where virtually no actuation force is required to maintain the position of the rocker sub-assembly.

Compared to prior art devices, an important advantage of the SVVA is its simplicity. The input and output oscillators of prior art continuously variable valvetrain devices, such as the SSCR and the DCDVVT, have been combined into one moving part. Due to its inherent simplicity, the SVVA differs significantly from the original SSCR device in its assembly procedure for mass production. With only one oscillating member per cylinder, the present invention accrues significant cost, manufacturing, and mechanical advantages over these previous designs. Further, a VVA device in accordance with the present invention does not “hang” from the camshaft, as is the case with these other mechanisms, but rather is supported on an engine head by its own arbors and journals, and therefore is not parasitic on the camshaft. Because there are fewer mechanical parts, there are fewer degrees of freedom in the mechanism. This simplifies the task of design optimization to meet performance criteria by substantially reducing the number of equations required to describe the motion of the present device. With its cost advantages and design flexibility, the present device can easily be applied to the intake camshaft of a gasoline engine for low cost applications, or to both the intake and exhaust camshafts of a diesel or a gasoline HCCI engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 a is an elevational drawing of a valvetrain equipped with the variable valve actuation system described in the parent application, showing the variable valve actuation system in maximum lift position and the valve in the fully closed position;

FIG. 1 b is a drawing like that shown in FIG. 1 a, showing the variable valve actuation system in maximum lift position and the valve in the fully open position;

FIG. 2 a is a drawing like that shown in FIG. 1 a, showing the variable valve actuation system in minimum lift position and the valve in the fully closed position;

FIG. 2 b drawing like that shown in FIG. 2 a, showing the variable valve actuation system in minimum lift position and the valve in the fully open position;

FIG. 3 is an isometric drawing of four valvetrains for a four-cylinder engine bank, each of the valvetrains being equipped with the variable valve actuation system described in the parent application linked together;

FIG. 4 is a graph showing a family of lift curves for a valvetrain equipped with the variable valve actuation system as shown in FIG. 3, the curves being bounded by maximum lift of the apparatus shown in FIGS. 1 a and 1 b, and by minimum lift of the apparatus shown in FIGS. 2 a and 2 b;

FIG. 5 is an isometric view of a module of a variable valve actuation system having a crank-based actuation transmission in accordance with the present invention, arranged for parallel operation of dual valves for a single engine cylinder;

FIG. 6 a is a schematic cross-sectional view of the system shown in FIG. 5 with the system at full valve lift; and

FIG. 6 b is a schematic cross-sectional view of the system shown in FIG. 5 with the system at minimum valve lift.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 a through 3, an exemplary prior art mechanical system for variable valvetrain actuation (SVVA), substantially as disclosed in pending U.S. patent application Ser. No. 11/294,223, filed Dec. 5, 2005 is shown. In FIGS. 1 a,1 b,2 a,2 b,5,6 a, and 6 b, only the components required for one cylinder's worth (one module) of an internal combustion engine are depicted. As shown in FIG. 3, for adjacent cylinders within an engine's cylinder head, additional modules 200 are placed and connected end-to-end by a carrier shaft primary crank assembly to provide variable valve timing control for all cylinders within the head.

High lift valve events with full duration are produced by the prior art SVVA mechanism 100 whenever its carrier shaft rocker pivot pins 1 are positioned as far as possible away from the input camshaft 2, as indicated in FIGS. 1 a and 1 b.

In operation, as the input camshaft 2 rotates clockwise, the opening flank 3 of the cam lobe 4 pushes the rocker roller 5 away, causing the rocker subassembly 6 to rotate in a clockwise direction. As the rocker subassembly 6 rotates, it turns about one of the carrier shaft rocker pivot pins 1 of the lift carrier shaft assembly 7, which are located at each of the engine's cylinders (not shown). A mating babbit or needle pivot bearing insert 8 facilitates the rotation of rocker subassembly 6.

Clockwise rotation of rocker subassembly 6 advances the output cam profiles 9,10 ground onto rocker flanges 11,12 to where the radius of the output cam opening flank 13 increases beyond that of the base circle portion 14 of the cam profile. The further that rocker subassembly 6 is rotated clockwise about the carrier shaft rocker pivot pin 1, the greater the lift imparted through the finger follower rollers 15. The left end of each finger follower 16 pivots about the ball shaped tip 17 of a conventional hydraulic valve lash adjuster 18 mounted in the engine head. Pushing downward on the centrally located finger follower roller 15 imparts lift to an engine valve 19 via the curved pallet surface 20 at the right end of finger follower 16.

When the carrier shaft assembly 7 is in the full lift position, as shown in FIGS. 1 a, and 1 b, maximum lift of engine valves 19 is reached whenever the rocker roller 5 reaches the nose portion 21 of the input cam 2. At this point, the rocker subassembly 6 ceases movement in the clockwise direction. As the input cam lobe 4 rotates still further in the clockwise direction, the nose portion 21 of the camshaft 2 slips past the rocker roller 5, and a helical torsion return spring 22 forces the rocker subassembly 6 to rotate counter-clockwise. This counter-clockwise rotation, in turn, reduces valve lift produced by the output cam profiles 9,10 and the finger follower rollers 15.

Eventually, as camshaft 2 continues to rotate clockwise, the rocker roller 5 reaches the constant radius portion 23 of the input cam lobe, where lift remains at zero until the next engine event occurs for that cylinder. The motion described above produces a peak lift profile 102 (FIG. 4) to maximize gas flow to the engine.

Short shank pins 24 of the carrier shaft assembly 7 ride in matching holes (not shown) bored through the engine's camshaft bearing towers which are integral to the cylinder head. Rotation of the carrier shaft assembly 7 about the center of these holes will vary engine load. Note that the carrier shaft shank pin axes 25 coincide with the finger follower roller axes 26 whenever they are on the base circle portions 14 of the output cam profiles 9,10, as shown in FIGS. 1 a and 2 a.

Note further that carrier shaft assembly 7 defines, and is synonymously referred to herein as, a primary crank mechanism (PCM) 7 for varying the position of rocker sub-assembly 6.

Referring to FIGS. 1 a, 1 b, 2 a and 2 b, if the PCM 7 is rotated clockwise through about 20° from its full load position, the mechanism produces progressively lower lift events with reduced duration (see FIG. 4). In the full 20° rotation position (FIGS. 2 a and 2 b), the carrier shaft rocker pivot pins 1 are in their closest proximity to the input camshaft 2.

Likewise, when the PCM 7 is in the light load position (FIGS. 2 a and 2 b), the finger follower roller 15 spends most of its time on the base circle portion 14 of the output cam profiles 9,10, just barely reaching the opening flank 13 of the profile, whenever the rocker roller 5 is aligned with the nose portion 21 of the input camshaft 2. Thus, the SVVA mechanism produces progressively shorter and shallower lift events, which minimize gas flow to the engine, culminating in lowest-lift profile 104 (FIG. 4). Varying the PCM 7 between the full load position first illustrated and the minimum load position described above produces the remaining lift curves within the family, as depicted in FIG. 4.

Referring to FIGS. 5, 6 a, and 6 b, a secondary crank mechanism (SCM) 27 is shown for actuating the SVVA mechanism 300. A presently preferred SCM 27, also referred to synonymously herein as an EVVAT, comprises a pair of connecting rods 29 pivotably linked to each pair of SVVA control shaft arms 31 by a connecting rod pin 28. Each connecting rod 29 is provided with a circular opening at the outer end 40 thereof defining a bearing journal for a circular lobe 32 integral to an actuator control shaft 33 eccentrically attached to lobe 32 and driven preferably and conventionally by an electric motor (not shown). Large diameter section 36 separates each pair of lobes 32 axially along actuator control shaft 33. Smaller diameter sections 34 ride in bearing journals also bored into the cylinder head's camshaft towers 35, and the larger diameter sections 36 serve to separate the lobe pairs 32. Preferably, babbit or needle bearing inserts 37,38 are provided at each end of each connecting rod 29 to facilitate rotating motion at the smaller connecting rod pin ends 39 and at the larger outer ends 40.

It will be seen that a lobe 32 and eccentrically-positioned actuator control shaft 33 define SCM 27, and that any analogous crank mechanism is comprehended by the present invention. The EVVAT crank mechanism just described is the presently preferred embodiment of a generic crank-based SCM 27 wherein the actuator control shaft 33 is a crank shaft and the lobe 32 is a crank throw. EVVAT 27 is a specialized case wherein the crankshaft axis of rotation 43 lies within the cross-sectional area of the crank throw. This arrangement provides a desirably large bearing surface between the crank throw and the connecting rod for absorbing torque reversal forces emanating from the engine's camshaft.

By optimizing the offset radius 41 of the actuator control shaft eccentrics 32, the position of the connecting rod pin 28 and the length of the connecting rods 29, an actuator shaft rotation of between about 160° and 175° can be provided to increase the limited rotational capability (˜20°) inherent in the prior art SVVA carrier shaft arms 31.

Moreover, the end positions of the eccentrics' motion can be designed to coincide with the points where the axes 42,43,44 of the connecting rod pin, actuator control shaft, and center of the eccentric radius, respectively, are collinear. Furthermore, when the two end states of the eccentrics' motion are arranged to correspond to full and minimum valve lifts, unwanted torque pulses cannot be transferred back to the actuator.

For example, as shown in FIG. 6 a, the center of an EVVAT eccentric radius 44 is collinear with the connecting rod pin axis 42 and the actuator control shaft axes 43, but farthest away in its motion (SCM 27 Top Dead Center, or TDC) from the input camshaft 2, yielding highest lift in the SVVA system, since the carrier shaft rocker pivot pin 1 is also in its farthest position from the camshaft 2. As the actuator control shaft 33 is rotated clockwise from this position, the connecting rods 29 apply forces to push the SVVA's carrier shaft arms 31 closer to the camshaft 2. In FIG. 6 b, rotation of actuator control shaft 33 has continued until the axes 42,43 of the connecting rod pin and the actuator control shaft are collinear with the eccentric center 44 (SCM 27 Bottom Dead Center, or BDC), but now the eccentric center 44 lies between them, and the carrier shaft rocker pivot pin 1 is closest to the camshaft 2, in its lowest lift position.

As shown in the end states of the eccentrics' motion (FIGS. 6 a and 6 b), with the important centers aligned as described above, the effective gear ratios are infinite. Careful optimization of the EVVAT arrangement can yield a useful range of effective gear ratios looking forward from the actuator control shaft (33) to the SVVA mechanism 100. Given today's internal combustion engine's packaging constraints, and a proper design, approximately mid-stroke through the eccentrics' travel can correspond to a minimum gear ratio as high as 7:1. Typically, the camshaft torque reversal forces encountered within the SVVA mechanism are their highest when it is in its full lift position. With the centers aligned as described above in the full lift end state of the SCM EVVAT crank system (as in FIG. 6 a), resulting forces transmitted through the connecting rods 29 are perpendicular to the actuator control shaft 33 and are directed through the actuator control shaft axis 43; thus, virtually no actuator torque is required to maintain this position. This is highly desirable from the standpoint of electric motor size and power consumption, and is an important and novel benefit of the present invention.

Although the SVVA mechanism forces are typically at their lowest when in the BDC minimum lift position (FIGS. 2 a, 2 b, and 6 b), having an infinite gear ratio is desirable for yielding the highest possible actuator/lift resolution.

While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims. 

1. A variable valve actuation system for inclusion in an internal combustion engine, comprising: a) a variable valve actuation sub-assembly disposed between a camshaft and a roller finger follower to variably actuate an associated engine combustion valve to vary the timing of valve opening, timing of valve closing, and amplitude of valve lift; and b) a crank-based transmission operatively attached to said variable valve actuation sub-assembly for selective actuation thereof.
 2. A system in accordance with claim 1 wherein said variable valve actuation sub-assembly comprises: a) a pivot shaft having a first axis disposed parallel to an axis of rotation of said camshaft defined as a second axis; b) a rocker sub-assembly pivotably disposed on said pivot shaft for rotation about said first axis, said rocker sub-assembly having a follower for following a lobe of said camshaft and having an output cam for engaging said roller finger follower; and c) a primary crank mechanism pivotably supportive of said rocker sub-assembly and said pivot shaft for varying the distance of said first axis from said second axis to vary the action of said output cam upon said one of said roller finger followers to vary said timing and lift of said associated valve, said primary crank mechanism being pivotable about a third axis outside of said pivot shaft.
 3. A system in accordance with claim 1 wherein said primary crank mechanism further comprises: a) a control shaft segment for said rocker sub-assembly wherein said third axis is the axis of said control shaft segment; and c) at least one rocker control arm connected between said pivot shaft and said rocker control shaft segment.
 4. A system in accordance with claim 3 wherein said crank-based transmission comprises: a) a connecting rod pivotably connected at a first end thereof to said rocker control arm and having a bearing journal formed at a second end thereof; and b) a secondary crank mechanism including a circular lobe rotatably disposed in said bearing journal and a transmission control shaft disposed eccentrically on said circular lobe, said transmission control shaft being mounted for rotation on said engine for rotating said pivot shaft, said rocker control arm, and said rocker control shaft segment about said third axis.
 5. A system in accordance with claim 4 further comprising an electric motor coupled to said transmission control shaft for rotation thereof to variably position said rocker sub-assembly with respect to said camshaft, via said circular lobe, said connecting rod, and said rocker control arm.
 6. A system in accordance with claim 3 further comprising a bias spring disposed between said rocker sub-assembly and said rocker control arm for maintaining contact of said roller with said cam lobe.
 7. A system in accordance with claim 1, wherein said engine includes a plurality of cylinders, valves, cam lobes, and roller finger followers defining an inline bank of cylinders, and wherein a variable valve actuation sub-assembly and a crank-based transmission is associated with each of said plurality of cylinders.
 8. A variable valve actuation system for use in an internal combustion engine having a plurality of inline cylinders, the system being included between a camshaft and a plurality of roller finger followers for variably actuating a plurality of associated engine combustion valves to vary the timing of valve opening, timing of valve closing, and amplitude of valve lift, the system comprising for each of said plurality of inline cylinders a variable valve actuation sub-assembly and a crank-based variable valve actuation transmission operatively attached to said variable valve actuation subassembly for selective actuation thereof.
 9. An internal combustion engine, comprising: a) a camshaft; b) a valvetrain including a plurality of combustion valves; c) a plurality of roller finger followers disposed between said camshaft and said combustion valvetrain; and d) a variable valve actuation system disposed between said camshaft and said plurality of roller finger followers, including a variable valve actuation sub-assembly and a crank-based variable valve actuation transmission operatively attached to said variable valve actuation sub-assembly for selective positioning of said variable valve actuation sub-assembly with respect to said camshaft. 